feat(smartduplex): improve backpressure handling and web/node stream interoperability

test/test.webduplexstream.both.ts

@@ -0,0 +1,144 @@
+import { expect, tap } from '@push.rocks/tapbundle';
+import { WebDuplexStream } from '../ts_web/index.js';
+
+// Helper: collect all chunks from a readable
+async function collectAll<T>(reader: ReadableStreamDefaultReader<T>): Promise<T[]> {
+  const results: T[] = [];
+  while (true) {
+    const { value, done } = await reader.read();
+    if (done) break;
+    results.push(value);
+  }
+  return results;
+}
+
+// =============================================
+// Basic transform
+// =============================================
+
+tap.test('WebDuplexStream: should transform chunks via writeFunction', async () => {
+  const stream = new WebDuplexStream<number, number>({
+    writeFunction: async (chunk, { push }) => {
+      push(chunk * 2);
+    },
+  });
+
+  const writer = stream.writable.getWriter();
+  const reader = stream.readable.getReader();
+
+  // Read and write concurrently to avoid backpressure deadlock
+  const readPromise = collectAll(reader);
+  await writer.write(5);
+  await writer.write(10);
+  await writer.close();
+  const results = await readPromise;
+
+  expect(results).toContain(10);
+  expect(results).toContain(20);
+});
+
+// =============================================
+// writeFunction return value
+// =============================================
+
+tap.test('WebDuplexStream: should enqueue returned non-null values', async () => {
+  const stream = new WebDuplexStream<string, string>({
+    writeFunction: async (chunk) => {
+      return chunk.toUpperCase();
+    },
+  });
+
+  const writer = stream.writable.getWriter();
+  const reader = stream.readable.getReader();
+
+  const readPromise = collectAll(reader);
+  await writer.write('hello');
+  await writer.close();
+  const results = await readPromise;
+
+  expect(results[0]).toEqual('HELLO');
+});
+
+// =============================================
+// fromUInt8Array
+// =============================================
+
+tap.test('WebDuplexStream: fromUInt8Array should produce data', async () => {
+  const data = new Uint8Array([1, 2, 3, 4, 5]);
+  const stream = WebDuplexStream.fromUInt8Array(data);
+  const reader = stream.readable.getReader();
+
+  const { value } = await reader.read();
+  expect(value).toBeTruthy();
+  expect(value.length).toEqual(5);
+});
+
+// =============================================
+// readFunction
+// =============================================
+
+tap.test('WebDuplexStream: readFunction should supply data to the stream', async () => {
+  const stream = new WebDuplexStream<string, string>({
+    readFunction: async (tools) => {
+      await tools.write('chunk1');
+      await tools.write('chunk2');
+      tools.done();
+    },
+    writeFunction: async (chunk, { push }) => {
+      push(chunk.toUpperCase());
+    },
+  });
+
+  const reader = stream.readable.getReader();
+  const results = await collectAll(reader);
+
+  expect(results).toContain('CHUNK1');
+  expect(results).toContain('CHUNK2');
+});
+
+// =============================================
+// finalFunction
+// =============================================
+
+tap.test('WebDuplexStream: finalFunction should emit final data', async () => {
+  const stream = new WebDuplexStream<string, string>({
+    writeFunction: async (chunk) => {
+      return chunk;
+    },
+    finalFunction: async (tools) => {
+      tools.push('final');
+      return undefined;
+    },
+  });
+
+  const writer = stream.writable.getWriter();
+  const reader = stream.readable.getReader();
+
+  const readPromise = collectAll(reader);
+  await writer.write('hello');
+  await writer.close();
+  const results = await readPromise;
+
+  expect(results).toContain('hello');
+  expect(results).toContain('final');
+});
+
+// =============================================
+// No writeFunction = passthrough
+// =============================================
+
+tap.test('WebDuplexStream: no writeFunction should passthrough', async () => {
+  const stream = new WebDuplexStream<string, string>({});
+
+  const writer = stream.writable.getWriter();
+  const reader = stream.readable.getReader();
+
+  const readPromise = collectAll(reader);
+  await writer.write('pass');
+  await writer.close();
+  const results = await readPromise;
+
+  expect(results[0]).toEqual('pass');
+});
+
+export default tap.start();